1. Field of the Invention
The present invention relates to a method of operating a catalytic converter which incorporates a heater. More specifically, the present invention pertains to a method of operating a catalytic converter in which the temperature of a heater is raised quickly at the initial stage of the operation of an engine to activate the catalyst and thereby achieve an increase in the exhaust gas conversion and in which the level of power is reduced after the desired temperature has been reached.
2. Description of the Related Art
Catalytic converters for use in controlling automotive exhaust gas have a minimum temperature that allows its catalyst function properly. Hence, the catalyst must be heated when the temperature thereof is not sufficiently high, i.e., at the beginning of running of a vehicle.
An example of such a catalytic converter has been introduced in SAE Paper 900503. This catalytic converter has a size of 480 cc, and includes a heater with a catalyst carried thereon. When the heater is energized by power of 3 KW while oxygen is being supplied thereto, the energization of which is started before the operation of the engine is started, the exhaust gas conversion at the beginning of the operation of the engine of a vehicle can be increased.
However, in the above-described catalytic converter operating method, it takes sixty seconds for the heater to be heated to 350.degree. C. despite of the large power consumption due to the relatively large foil type heater. This results in a reduced exhaust gas conversion. Furthermore, it is difficult in a practical operation to energize the heater before the engine is operated. Also, the above literature does not refer to the amount of exhaust gas which can be controlled by the above catalytic converter, the temperature at which the catalyst functions, or the energization method. Furthermore, telescope phenomenon, inherent to the foil type heater, readily occurs in this heater, easily causing faulty operation thereof.